In Manitoba, fields between Riding Mountain National Park and Duck Mountain Provincial Park were hit with sustained frosts.

“There are a few areas where they had a long duration of a light frost and that’s as bad as a short duration of a really hard frost,” said Anastasia Kubinec, manager of crop industry development with Manitoba Agriculture at Carman, Man.

A long frost allows enough time for cell walls to break open and for desiccation to occur in canola and soybean pods and in ears of corn, she said.

“So, it potentially causes some major damage if some of the plants are not at the stage where they are swathed or ready to be combined; they are not at that physiological maturity.”

Areas most affected included Swan River, which had eight hours of frost, Inglis (seven hours), Birtle (six hours) and Oakburn, which recorded lows of -4 C.

“So we’re quite concerned about crops around Oakburn and what stage they’re at,” said Kubinec.

In Saskatchewan, provincial extension specialist Brent Flaten said the eastern side of the province was worst hit. However, he said he doesn’t expect there will be a lot of damage because most crops are mature enough to withstand it.

“A lot of the crops are either combined or quite mature, so we aren’t really sure how much damage there’ll be.”

It will take a few days for crop advisers to get into fields to better assess the aftermath.

Late-seeded canola could be affected with green seed and farmers might start to see pods opening in a day or two, he said. “But it’s only with the very late crops.

“All I know is, that it is a localized area, spotty area; everything in that P.A. (Prince Albert), to Regina and east,” said Flaten, who’s based in Moose Jaw.

He’s not yet sure how soybeans will be affected, if at all.

In one of the worst-hit areas, around Broadview, Environment Canada reported five hours of frost and two hours of temperatures below -4 C. Later-maturing crops in this region are likely to see issues, he said.

Back in Manitoba, Kubinec said canola, soybeans and silage corn are likely to be most affected, but much depends on the stage of plant development in each field.

“Those soybeans though, talking to a lot of agronomists in the area, they’re starting to see leaf-colour change and leaf drop,” she said.

Many soybean fields are drying down naturally and farmers may see an issue with green seed once they start combining.

“There’s nothing they can do about that,” she said.

Canola growers, however, might want to go ahead and swath crops if they’re ready, she said. Farmers might have to put up with a little yield loss or lower test weights, but swathing now will reduce shattering and that is likely better than leaving it.

Canola in swaths will likely get moisture from dew, which will hopefully slow dry down and prevent pods from opening, she said.

Growers who straight-cut shatter-resistant canola varieties will likely see no problems because those varieties should dry down without pads opening, although she said she was calling for more information.

On grain corn for silage, Kubinec encouraged producers to make sure they have their feed tested for nitrates. Feed with high nitrate levels is poisonous to cattle.

Producers will have to evaluate how quickly they can take the crop off while maintaining its feed value and tonnage. Corn leaves dry down rapidly following frost and that reduces tonnage.

She expected to have updated reports from the affected areas later Wednesday.

Crop updates were not available for Alberta.

— Terry Frieswrites for Commodity News Service Canada, a Glacier FarmMedia company specializing in grain and commodity market reporting.